It is well known to the skilled person that pyrotechnical processes may release large quantities of energy in a short time, and/or produce gases, light, sound or a combination of these.
Pyrotechnical devices are commonly used to obtain a quick activation of various devices. As an example, in the automotive industry pyrotechnical devices are utilized in order to quickly activate safety devices in a vehicle, such as an airbag or a seat belt tensioner.
An example of a vehicle utilizing pyrotechnical devices, is a vehicle comprising a deployable bonnet. The bonnet covers an engine compartment and is connected to the vehicle by hinge arrangements, such that the bonnet can be opened in order to allow access to the engine compartment for maintenance and/or repair. If the vehicle is involved in an accident, in which the front part of the vehicle hits a vulnerable road user, such as a pedestrian or bicyclist, it is not uncommon that the vulnerable road user is thrown onto the bonnet of the vehicle and that the head of the vulnerable road user impacts on the bonnet. In order to reduce the severity of these accidents, it is known to use a deployable bonnet. By raising at least the rear part of the bonnet to an “impact position”, a so called deployed position or pop-up position, the distance between the bonnet and any hard engine parts is increased. The bonnet may be lifted to the deployed position by means of an inflatable member such as an airbag, which may be activated by a pyrotechnical device. The airbag may further be utilized to cover a portion of the windscreen and/or A-pillars.
There may also be pyrotechnical devices located at the hinge arrangements in order to change the functional mode of the hinge arrangements, such that the bonnet is allowed to be displaced to the deployed position. The pyrotechnical devices may e.g., be activated to release a release pin, thereby allowing previously locked hinge arrangement members to move in relation to each other.
The vehicle comprising the deployable bonnet may hence comprise three pyrotechnical devices, one for activation of the airbag raising the bonnet, and one at each hinge arrangement for changing its functional mode, such that the bonnet is allowed to be raised to the deployed position. However, utilizing three different pyrotechnical devices may make the arrangement expensive and/or difficult to mount in the vehicle at the production facility.
An alternative to using three pyrotechnical devices is to instead use only one pyrotechnical device, e.g., located at the airbag, which via a complicated mechanical release system, e.g., comprising bars, wires, and/or release elements, can change the functional mode of the hinge arrangement, such that the bonnet may assume the deployed position. However, such a mechanical release system involves many different parts, which makes the arrangement heavy and may require large packaging volume, as well as making the arrangement expensive and difficult to mount in the vehicle at the production facility.